1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, an image processing program, and a computer-readable storage medium storing image processing program code, and more particularly, to image-data sending/receiving processing according to the traffic on a communication network.
2. Description of the Related Art
Cellular telephones (or portable terminals) are now being widely used. FIG. 1 illustrates a typical example of a communication system using portable terminals.
In FIG. 1, portable terminals 401 and 405 each include a display unit, an operation unit, and a communication controller, and communicate with a relay device (base station) 403 via communication channels 402 and 404.
Modulation methods are rapidly shifting towards the use of digital data rather than analog data, and portable terminals are being increasingly used not only as telephones for sending and receiving audio data, but also as portable terminals for sending and receiving data. Additionally, along with increases in the transmission rate, video (moving pictures) can be sent and received, which is impossible in the known art, and it is expected that such portable terminals will be used as video phones.
FIG. 2 is a block diagram illustrating a known video phone system. In FIG. 2, a video camera 501 captures an image of, for example, a character, and outputs a video signal. A microphone 504 receives sound and outputs an audio signal.
Analog-to-digital (A/D) converters 502 and 505 convert the signals output from the video camera 501 and the microphone 504, respectively, into digital signals.
A video encoder 503 encodes the digital video signal output from the A/D converter 502 according to a known compression/encoding method, and an audio encoder 506 encodes the digital audio signal output from the A/D converter 505 according to a known compression/encoding method. Generally, compressed and encoded data is referred to as a “bitstream”.
A multiplexer 507 multiplexes the video bitstream and the audio bitstream so that they can be played back in synchronization with each other, thereby generating a single bitstream.
A demultiplexer 508 demultiplexes the multiplexed bitstream into the video bitstream and the audio bitstream. Then, a video decoder 509 decodes the video bitstream, a digital-to-analog (D/A) converter 510 converts the digital video data into an analog signal, and a monitor 511 displays the decoded video signal.
An audio decoder 512 decodes the audio bitstream, a D/A converter 513 converts the digital audio data into an analog signal, and a speaker 514 outputs the decoded sound.
A communication controller 515 sends and receives the above-described bitstreams. Reference numeral 516 indicates a communication channel, which is a wireless channel in this example. A relay device (base station) 517 sends and receives data to and from portable terminals. Reference numeral 518 indicates a communication channel 518 via which the relay device 517 and the portable terminals communicate with each other. A synchronization controller 519 controls the video signal and the audio signal to be played back in synchronization with each other by using timing control information superposed on each bitstream.
In the above-described known video phone system, however, depending on the traffic on the communication network, pictures or sound may not be continuously received at a receiving side, thereby failing to properly transmit information.